ABS molding composition having improved crack and chemical resistance and its use

ABSTRACT

Thermoplastic molding composition scan be advantageously used in hydrofluoro olefin containing areas, comprising components A, B, C and, D: 10 to 35 wt.-% ABS graft rubber A obtained by emulsion polymerization, 50 to 75 wt.-% SAN copolymer B, 4 to 20 wt.-% copolymer C from ethylene and C 1 -C 6 -alkyl(meth)acrylate, and 4 to 20 wt.-% ABS graft rubber copolymer D obtained by mass polymerization.

The invention is directed to ABS molding compositions that exhibitimproved environmental stress crack resistance properties in thepresence of olefinic unsaturated blowing agents, such as hydrofluoroolefins (HFO). The invention further deals with their use in hydrofluoroolefin containing areas and as inner liner in cooling apparatuses.

For thermoformed equipment liners e.g. of refrigerators, styrenecopolymers, and in particular ABS resins are often the material ofchoice for their balance of properties: strength, toughness (impactresistance), appearance (gloss and color), chemical resistance,processability, and price. Sheet extrusion grades of ABS provide deepdraw capability for thermoforming operations, strength and toughness fordurability in assembly and use, high gloss, stain and chemicalresistance to items such as food.

Document KR-A 2006131373 describes a heat resistant ABS moldingcomposition comprising from 20 to 35 parts by weight of an ABS graftrubber (A), 0.1 to 10 parts by weight of an ethylene-alkyl(meth)acrylatecopolymer (e.g. Elvaloy® AC) (B) and 84.9 to 55 parts by weight of amixture (C) of two SAN copolymers (c1(long chain) and c2 (branched), ANcontent 20% by weight (wt.-%), each). The ABS polymer blend is used foroutdoor applications (automobile parts, building materials etc.) and hasan improved chemical and crack resistance against insecticides andcleaning agents. The application of the ABS polymer composition incooling apparatuses is not addressed.

The refrigeration industry uses polyurethane foam for heat insulationbetween the outer metal cabinet and the inner plastic liner. Thepolyurethane requires a blowing agent to generate the foam. The choiceof a blowing agent is a complicated matter that depends on many factorsincluding thermal conductivity, cost, flammability, toxicity, andenvironmental factors such as ozone depletion and global warmingpotential. When used as refrigerator liners, the ABS resin is alsoexposed to foamed-in-place insulation during assembly. Foamed-in-placeinsulation typically generates a rush of chemical blowing agent (onechemical or mixtures of different chemicals) so as to foam theinsulating material (e.g. polyurethane).

As ABS liners are exposed to the blowing agent, the ABS resin has to bedesigned and composed in a way that it provides chemical resistanceagainst the applied blowing agent. Otherwise it will degrade the ABSmaterial, when getting in contact with the liner, causing it to crack.To date, several ABS compositions were invented that show good stresscracking resistance against commonly used foam blowing agents such aschlorofluorocarbons (CFC), hydrochlorofluorocarbons (HCFC),hydrofluorocarbons (HFC), and hydrocarbons (e.g. cyclopentane).

US 2008/0093578 discloses a thermoplastic resin composition for arefrigerator, comprising an ABS graft copolymer resin (A) obtained byemulsion polymerization, a styrenic copolymer (B) comprising (b1) acopolymer prepared by copolymerizing polybutadiene with acrylonitrileand styrene and (b2) a copolymer prepared by copolymerizingpolybutadiene with styrene, and a SAN-copolymer (C). Said resincomposition is stress crack resistant against HCFC.

In regard to the environmental factors, particularly global warmingpotential, a new class—the “Fourth Generation”—of blowing agents wasdeveloped that contains olefinic unsaturation. The unsaturation in thestructure of these so-called HFOs (hydrofluoro olefins, e.g.trans-1-chloro-3,3,3-trifluoropropene, trade name Solstice® LBA,Honeywell or Forane® 1233zd, Arkema as well as(Z)-1,1,1-4,4,4-hexafluorobutene, FHO-1336mzz-Z trade name Formacel®1100, Chemours) cause them to readily decompose in the atmosphere in amatter of days rather than hundreds of years, thereby minimizing harmfulglobal warming. However, although these HFO blowing agents have someappealing advantages, they appear to be more susceptible to causeenvironmental stress cracks and damage to the ABS material comprised inthe inner liner of a refrigerator.

US 2014/019090978 describes refrigerators which are insulated with apolyurethane foam in which the blowing agent comprises substantially1-chloro-3,3,3-trifluoropropene. Preferably the inner liner of therefrigerator is formed in large part from High Impact Polystyrene(HIPS). Further suitable materials from which the liner may be formed atleast partly are GPPS, styrene copolymers, such as styrene-butadieneblock copolymers, ASA, ABS, polyolefins, (meth)acrylates such as PMMA,PC, PVC, PET and mixtures of these. In all examples only HIPS alone hasbeen used.

For application of this new type of blowing agent, an ABS resin isneeded that provides not only most of the favorable properties known forABS material like strength, toughness (impact resistance), appearance(gloss and color), processability, and price but in particular showshigh stress crack resistance against olefinic blowing agents or mixturescontaining olefinic blowing agents.

The formation of aggressive environmental stress cracks due to thepresence of HFO against ABS resins and its potential to reduce thelifetime of ABS resin inner liners in cooling apparatuses is the problemaddressed by the present invention.

It is one object of the invention to provide ABS resin compositionssuitable for inner liners of cooling apparatuses that show most of thefavorable properties known for ABS materials and exhibit in particularimproved environmental stress crack resistance (ESCR) properties inpresence of olefinic unsaturated blowing agents, in particular inpresence of hydrofluoro olefins (HFO). The compositions used in thepresent invention show this superior property profile.

One aspect of the invention is the use of a thermoplastic moldingcomposition in hydrofluoro olefin containing areas, comprising (orconsisting of) components A, B, C and, if present, D:

(A) 10 to 35% by weight of at least one graft rubber copolymer Aobtained by emulsion polymerization and built up from

-   -   (a₁) 30 to 90% by weight, based on (A), of at least one graft        base (a₁) made from        -   (a₁₁) 70 to 98% by weight, based on (a₁), of at least one            diene, in particular 1,3-butadiene, and        -   (a₁₂) 2 to 30% by weight, based on (a₁), of at least one            monomer selected from the group consisting of: styrene,            α-methylstyrene, acrylonitrile, methacrylonitrile and methyl            methacrylate, in particular styrene; and    -   (a₂) 10 to 70% by weight, based on (A), of a graft (a₂), grafted        onto the graft base and built up from        -   (a₂₁) 65 to 95% by weight, based on (a₂), of at least one            vinylaromatic monomer, in particular styrene,        -   (a₂₂) 5 to 35% by weight, based on (a₂), acrylonitrile            and/or methacrylonitrile, preferably acrylonitrile, and        -   (a₂₃) 0 to 20% by weight, based on (a₂), of at least one            monomer selected from the group consisting of:            C₁-C₄-alkyl(meth)acrylates, maleic anhydride, N-phenyl            maleimide, N-cyclohexyl maleimide and (meth)acrylamide;

(B) 50 to 75% by weight of at least one copolymer B made from

-   -   (b₁) 50 to 95% by weight, based on (B), of at least one        vinylaromatic monomer, preferably styrene or α-methylstyrene,        more preferred styrene, and    -   (b₂) 5 to 50% by weight, based on (B), acrylonitrile and/or        methacrylonitrile, preferably acrylonitrile, and    -   (b₃) 0 to 20% by weight, based on (B), of one or more of the        monomers as described for (a₂₃),

(C) 4 to 20% by weight of at least one copolymer C made from

-   -   (c₁) 70 to 91% by weight, based on (C), ethylene,    -   (c₂) 9 to 30% by weight, based on (C), at least one, preferably        one, C₁-C₆-alkyl(meth)acrylate, preferably C₁-C₆-alkylacrylate,        more preferred methyl-, ethyl- and/or n-butylacrylate, most        preferred methyl- and/or ethylacrylat, in particular        methylacrylate, and    -   (c₃) 0 to 15% by weight, based on (C), of at least one further        comonomer copolymerizable with (c1) and (c2), preferably        selected from the group consisting of: carbon monoxide,        alpha-olefins such as propene and/or (meth)acrylic acid,        glycidyl (meth)acrylate;

(D) 0 to 20% by weight of at least one graft rubber copolymer D obtainedby mass polymerization and built up from

-   -   (d₁) 10 to 25% by weight, based on (D), of at least one graft        base (d₁) made from        -   (d₁₁) 75 to 100% by weight, based on (d₁), of at least one            diene, in particular 1,3-butadiene, and        -   (d₁₂) 0 to 25% by weight, based on (d₁), of at least one            vinylaromatic monomer, preferably styrene or            α-methylstyrene, more preferred styrene, and    -   (d₂) 75 to 90% by weight, based on (D), of a graft (d₂), grafted        onto the graft base and built up from        -   (d₂₁) 68 to 82%, preferably 70 to 80%, by weight, based on            (d₂), of at least one vinylaromatic monomer, preferably            styrene or α-methylstyrene, more preferred styrene,        -   (d₂₂) 18 to 32%, preferably 20 to 30%, by weight, based on            (d₂), acrylonitrile or methacrylonitrile, preferably            acrylonitrile, and        -   (d₂₃) 0 to 20% by weight, based on (d₂), of one or more of            the monomers as described for (a₂₃);

wherein the sum of components A, B, C and D totals 100% by weight.

According to the invention the term “mass polymerization” means a bulkor solution polymerization or a suspension polymerization in which thepolymerization is started as before mentioned as bulk or solutionpolymerization and is then continued after suspension in water to finalconversion.

In accordance with the invention the afore-mentioned molding compositionis preferably used for the preparation of inliners for coolingapparatuses, in particular refrigerators.

The term “wt.-%” is identical to “% by weight”. The term “pbw” isidentical to “parts by weight”.

The minimum amount of the optional component D is 0.01%, preferably0.05%, more preferred 0.10%, by weight. If in said thermoplastic moldingcomposition optional component D is present, and/or the amounts ofcomponents A and/or C are further specified, the amount of component Bis set within the given range, provided that the amounts of components Ato D add up to 100% by weight.

The afore-mentioned thermoplastic molding compositions used inaccordance with the invention can further comprise optional components Eand/or F.

Component E is at least one inorganic additive E selected fromphyllosilicates (E1) and nano calcium carbonate (E2). Component E can beused in amounts of from 0.01 to 10 parts by weight, based on 100 partsby weight of the composition consisting of components A, B, C and D.

Component F is at least one further additive and/or processing aid F.Component F can be used in amounts of from 0.01 to 20 parts by weight,based on 100 parts by weight of the composition consisting of componentsA, B, C and D.

If in said thermoplastic molding composition optional components Eand/or F are present, the minimum amount of each of components E and Fis preferably 0.05, more preferred 0.10 parts by weight, based on 100parts by weight of the composition consisting of components A, B, C andD.

Preferably a thermoplastic molding composition is used in accordancewith the invention comprising (consisting of) components A, B, C and Din the following amounts:

(A): 18 to 28 wt.-%;

(B): 55 to 75 wt.-%;

(C): 6 to 15 wt.-%;

(D): 0 to 15 wt.-%;

wherein components A, B, C and D have the meaning as described for theuse before.

More preferred a thermoplastic molding composition is used in accordancewith the invention comprising (consisting of) components A, B, C, D inthe following amounts:

(A): 18 to 28 wt.-%;

(B): 55 to 70 wt.-%;

(C): 6 to 15 wt.-%;

(D): 0 to 15 wt.-%;

wherein components A, B, C and D have the meaning as described before.

According to a further preferred embodiment of the invention athermoplastic molding composition is used in accordance with theinvention comprising (consisting of) components A, B, C and D in thefollowing amounts:

(A): 10 to 35 wt.-%;

(B): 50 to 75 wt.-%;

(C): 4 to 20 wt.-%;

(D): 4 to 20 wt.-%;

wherein components A, B, C and D have the meaning as described before.

In particular preferred is the use of a molding composition consistingof components A, B, C and D in the amounts as hereinbefore defined.

Furthermore preferred are molding compositions used in accordance withthe invention consisting of components A, B, C, D and 1 to 20 parts byweight of component F, based on 100 parts by weight of the compositionconsisting of components A, B, C and D.

Furthermore preferred are molding compositions used in accordance withthe invention consisting of components A, B, C, D, and 0.01 to 10,preferably 0.01 to 8, more preferably 0.01 to 5 parts by weight ofcomponent E, based on 100 parts by weight of the composition consistingof components A, B, C and D.

Furthermore preferred are molding compositions used in accordance withthe invention consisting of components A, B, C, D and, based on 100parts by weight of the composition consisting of components A, B, C andD, 1 to 20 parts by weight of component F, and 0.01 to 10, preferably0.01 to 8, more preferably 0.01 to 5 parts by weight of component E.

A further aspect of the invention are thermoplastic molding compositionsfor use in hydrofluoro olefin containing areas comprising (or consistingof) components A, B, C, D:

(A): 10 to 35 wt.-%;

(B): 50 to 75 wt.-%;

(C): 4 to 20 wt.-%;

(D): 4 to 20 wt.-%;

wherein components A, B, C and D have the meaning as described for theuse of the thermoplastic molding composition above.

The afore-mentioned novel thermoplastic molding compositions accordingto the invention can further comprise optional components E and/or F inthe amounts as described above. All the definitions of components A, B),C), D) and optional components E) and F) given for the use of thethermoplastic molding composition in accordance with the inventionhereinbefore are also valid for the thermoplastic molding compositions.The afore-mentioned inventive molding composition can preferably be usedfor the preparation of inliners for cooling apparatuses, in particularrefrigerators.

Preferred is an inventive molding composition comprising (consistingof):

(A): 18 to 28 wt.-%;

(B): 55 to 70 wt.-%;

(C): 6 to 15 wt.-%;

(D): 6 to 15 wt.-%; wherein components A, B, C and D have the meaning asdescribed before.

More preferred is a molding composition as defined above comprising(consisting of):

(A): 18 to 28 wt.-%;

(B): 55 to 69 wt.-%;

(C): 6 to 15 wt.-%;

(D): 6 to 15 wt.-%;

wherein the sum of components A, B, C and D totals 100% by weight, andwhich further comprises 1 to 20 parts by weight of component F, based on100 parts by weight of the composition consisting of components A, B, Cand D.

A further aspect of the invention is the use of said thermoplasticmolding compositions for the preparation of inliners for coolingdevices, in particular refrigerators, as herein-before described.

Component A (Graft Rubber Copolymer A)

The at least one graft rubber copolymer A is used as an impact modifierand forms a soft phase having a glass transition temperature T_(g) of<0° C., preferably <−20° C., particularly preferably <−40° C. The glasstransition temperature T_(g) is measured by dynamic mechanical analysis(DMA) using a frequency of 1 Hz.

Preferably at least one graft copolymer A according to the invention isused which is built up from

a₁: 40 to 90 wt.-%, preferably 45 to 85 wt.-%, particularly preferably45 to 75 wt.-% of at least one graft base a₁, based on (A), made from:

-   -   80 to 98 wt.-%, preferably 85 to 97 wt.-%, based on (a₁), of at        least one diene (a₁₁), preferably 1,3-butadiene,    -   2 to 20 wt.-%, preferably 3 to 15 wt.-%, based on (a₁), of at        least one monomer (a₁₂), preferably styrene; and

a₂: 10 to 60 wt.-%, preferably 15 to 55 wt.-%, particularly preferably25 to 55 wt.-%, based on (A), of a graft a₂, grafted onto the graft basea₁ and built up from:

-   -   65 to 80 wt.-%, in particular 65 to 75 wt.-%, based on (a₂), of        at least one vinylaromatic monomer (a₂₁), in particular styrene,        and    -   20 to 35 wt.-%, in particular 25 to 35 wt.-%, based on (a₂), of        acrylonitrile and/or methacrylonitrile (a₂₂), preferably        acrylonitrile, and    -   0 to 20% by weight, based on (a₂), of at least one monomer        (a₂₃).

The diene a₁₁ is preferably 1,3-butadiene and/or isoprene, morepreferably 1,3-butadiene. The comonomer a₁₂ is preferably styrene. Thevinylaromatic monomer a₂₁ is preferably styrene and/or α-methylstyrene,more preferred styrene. Comonomer a₂₂ is acrylonitrile and/ormethacrylonitrile, preferably acrylonitrile. Further comonomer a₂₃ is atleast one monomer selected from the group consisting of:C₁-C₄-alkyl(meth)acrylates, maleic anhydride, N-phenyl maleimide,N-cyclohexyl maleimide and (meth)acrylamide, preferablyC₁-C₄-alkyl(meth)acrylates and maleic anhydride. Preferably comonomera₂₃ is not present.

The weight average particle diameter D_(w) of the at least one graftbase a1 of the graft copolymer A is generally 0.15 μm to 0.80 μm,preferably 0.15 to 0.50 μm, particularly preferably 0.20 μm to 0.50 μm,most preferably 0.25 to 0.40 μm.

One or more graft copolymers A with uni-, bi-, tri- or multimodalparticle size distributions can be used. The weight average particlediameter D_(w) can be determined by a measurement with anultracentrifuge (see W. Scholtan, H. Lange: Kolloid Z. u. Z. Polymere250, pp. 782 to 796 (1972)) or a disc centrifuge DC 24000 by CPSInstruments Inc. at a rotational speed of the disc of 24,000 r.p.m. Theparticle diameter can also be determined by static light scattering (seeA. Schmidt in Houben-Weyl, Methoden der Organischen Chemie, Georg ThiemeVerlag, Stuttgart, 1987, volume E20, pp. 238-248) wherein with thismethod in opposite to the two first no information about the particlessize distribution is obtained. For definition of the weight averageparticle size D_(w) see: G. Lagaly, O. Schulz, R. Zimehl: Dispersionenand Emulsionen: Eine Einführung in die Kolloidik feinverteilter Stoffeeinschließlich der Tonminerale, Darmstadt: Steinkopf-Verlag 1997, ISBN3-7985-1087-3, page 282, formula 8.3b.

Preferred diene rubbers (graft bases a₁) and graft copolymers A aredescribed in EP-B 0993476, in WO 2001/62848 A1 and in WO 2012/022710 (inparticular pages 23-28).

Processes for the preparation of the graft copolymers A are known to aperson skilled in the art and described in the literature. According tothe invention the graft base (a₁) and the graft copolymers A areobtained from free-radical emulsion polymerization (EP-B 993 476, WO2001/62848 and WO 2012/022710).

Suitable temperatures for the emulsion polymerization process aregenerally from 20 to 100° C., preferably 30 to 90° C. As emulsifiersthere may be used conventional emulsifiers for example, alkali metalsalts of alkyl- or alkylarylsulfonic acids, alkyl sulfates, salts ofhigher fatty acids having 10 to 30 carbon atoms, sulfosuccinates, ethersulfonates or rosin soaps from different natural raw materials.Preference is given to alkali metal salts, in particular the sodium andpotassium salts, of alkylsulfonates or fatty acids having 10 to 18carbon atoms.

Further preference is given to resin or rosin acid-based emulsifiers, inparticular alkaline salts of the rosin acids. Salts of the resin acidsare also known as rosin soaps. Examples include alkaline soaps as sodiumor potassium salts from disproportionated and/or dehydrated and/orhydrated and/or partially hydrated gum rosin with a content ofdehydroabietic acid of at least 30 wt.-% and preferably a content ofabietic acid of maximally 1 wt.-%. Furthermore, alkaline soaps as sodiumor potassium salts of tall resins or tall oils can be used with acontent of dehydroabietic acid of preferably at least 30 wt.-%, acontent of abietic acid of preferably maximally 1 wt.-% and a fatty acidcontent of preferably less than 1 wt.-%. Mixtures of the aforementionedemulsifiers can also be used for the production of the starting rubberlatices. The use of alkaline soaps as sodium or potassium salts fromdisproportionated and/or dehydrated and/or hydrated and/or partiallyhydrated gum rosin with a content of dehydroabietic acid of at leastwt.-% and a content of abietic acid of maximally wt.-% is advantageous.

In general, the emulsifiers are used in amounts of 0.5 to 5 wt.-%, inparticular from 0.5 to 4 wt.-%, based on the monomers used for thepreparation of the graft base a1.

Preferably for the preparation of the dispersion so much water is usedthat the finished dispersion has a solids content of 20 to 50 wt.-%.

For initiating the polymerization radical initiators are suitable, whichdecompose at the selected reaction temperature, i.e. those whichdecompose by heat alone, as well as those decomposing in the presence ofa redox system. The polymerization initiators used are preferably thoseforming free-radicals, such as peroxides, preferably peroxosulphates (assodium or potassium persulfate) and azo compounds such asazodiisobutyronitrile. Redox systems can also be used, in particularthose based on hydroperoxides, such as cumene hydroperoxide ortert-butyl hydroperoxide together with a reducing agent, e.g. succrose,dextrose and ferrous iron.

In general, the polymerization initiators are used in an amount of 0.05to 1 wt.-%, preferred 0.1 to 1 wt.-%, based on the graft base monomersa₁₁ and a₁₂.

The polymerization initiators and also the emulsifiers can be added tothe reaction mixture, either discontinuously as the total amount at thebeginning of the reaction, or, continuously divided into severalportions intermittently at the beginning and at one or more later timepoints during a specified time interval. Continuous addition may alsofollow a gradient, which can for example rise or decline and can belinear or exponential, or stepwise.

Further, molecular weight regulators such as, e.g.ethylhexylthioglycolate, n- or t-dodecyl mercaptan and other mercaptans,terpinols and dimeric alpha-methyl styrene or other suitable compoundsfor regulating the molecular weight can be used. The molecular weightregulators can be added to the reaction mixture batchwise orcontinuously, as described for the polymerization initiators andemulsifiers before.

To maintain a constant pH-value which is preferably from 6 to 12.5,preferred 7 to 12.0, buffer substances such as Na₂HPO₄/NaH₂PO₄, sodiumhydrogen carbonate, sodium carbonate or buffers based on citricacid/citrate, can be used additionally. Regulators and buffer substancesare used in the usual amounts.

In a particular preferred embodiment, during the grafting of the graftbase a₁ with the monomers a₂₁ and a₂₂ and optionally a₂₃ a hydroperoxideand a reducing agent are added together with ferrous iron.

The person skilled in the art selects the polymerization conditions, inparticular the type, quantity and dosage of the emulsifier and of theother polymerization auxiliaries so that the resultant rubber latex(graft base) a₁ of the graft copolymer A has an average particle size,defined by the weight average particle diameter D_(w) of from 0.15 μm to0.80, preferably 0.15 to 0.60 μm, particularly preferably 0.20 μm to0.50 μm, most preferably 0.25 to 0.40 μm.

In case of a monomodal particle size distribution the resultant particlediameter D_(w) of the polymer particles of the graft base a1 ispreferably from 0.20 μm to 0.50 μm, more preferably 0.25 to 0.40 μm.

One can also select the polymerization conditions so, that the polymerparticles of the graft base a₁ have a bi-, tri- or poly-modal particlesize distribution in the aforementioned ranges. A bi-, tri- or polymodalparticle size distribution can be achieved by a (partially)agglomeration of the graft base particles a₁.

Furthermore and preferred in accordance with the invention, to achieve abi-, tri- or polymodal particle size distribution of the graft rubbercopolymer (A), it is possible to prepare, separately from one another inthe usual manner, two or more different graft bases a₁₋₁), a₁₋₂) etc.differing in their weight average particle size D_(w), and to mix saidgraft bases a₁₋₁), a₁₋₂) etc. in the desired mixing ratio.

Advantageously first a graft base a₁ is prepared in the usual manner,which is then separately agglomerated in two or more batches to obtaintwo or more different graft bases a₁₋₁), a₁₋₂) etc. differing in theirparticle size D_(w). Afterwards the graft a₂ is grafted onto the mixtureof said (agglomerated) graft bases a₁₋₁), a₁₋₂) etc.

Preferred is the use of a graft rubber copolymer (A) having a bimodalparticle size distribution which is prepared from a mixture of a(n)(agglomerated) graft base a₁₋₁) of fine particles having a particle sizeD_(w) of from 0.15 to 0.30 μm, preferably 0.15 to 0.25 μm and a(n)(agglomerated) graft base a₁₋₂) of coarse particles having a particlesize D_(w) of from 0.40 to 0.80 μm, preferably 0.45 to 0.60 μm. Themixing ratio of graft bases a₁₋₁) to a₁₋₂) is preferably from 50/50 to90/10.

According to a particular embodiment, the graft base a₁ can be preparedby polymerizing the monomers a₁₁ to a₁₂ in the presence of a finelydivided latex (so-called “seed latex” polymerization). This latex isprovided and can be made of elastomeric polymers forming monomers orfrom other monomers such as those mentioned above. Suitable seed laticesconsist for example of polybutadiene or polystyrene.

In the seed polymerization usually first a finely divided polymer,preferably a polybutadiene, is produced as seed latex and then this seedlatex is further polymerized with monomers comprising butadiene intolarger particles (see Houben-Weyl, Methoden der Organischen Chemie,Makromolekulare Stoffe, Part 1, p. 339 (1961), Thieme Verlag,Stuttgart). It is preferably carried out using the seed batch process orusing the seed-feed process. Preferred graft bases a₁ and graftcopolymers A may be obtained by the seed polymerization technologydescribed in the document WO 2012/022710 A1.

In another preferred embodiment, the graft base a₁ is produced in aso-called feed process. In this method, a certain proportion of themonomers a₁₁ and a₁₂ is provided and the polymerization is started,after which the remainder of the monomers a₁₁ and a₁₂ (“feed portion”)is added as a feed during the polymerization.

The feed parameters (gradient shape, amount, duration, etc.) depend onthe other polymerization conditions. The addition of the radicalinitiator and emulsifier is as described before. Preferably in the feedprocess, the proportion of the monomers first provided is up to 50wt.-%, preferably up to 40 wt.-%, based on a₁. Preferably the remainderof the monomers a₁₁ to a₁₂ is fed within 1 to 18 hours, in particular 2to 16 hours, more preferred 4 to 12 hours.

In the second stage, the rubber latex is agglomerated. This can be doneby adding a dispersion of an acrylic ester copolymer as agglomerationagent. Preferably dispersions of copolymers made from (C1-C4alkyl)esters of acrylic acid, preferably of ethyl acrylate, and 0.1 to10 wt.-% monomers forming polar polymers such as acrylic acid,methacrylic acid, acrylamide or methacrylamide, N-methylolmethacrylamide or N-vinyl pyrrolidone, are used. Particularly preferredis a copolymer made from 96% ethyl acrylate and 4% of methacrylamide.The agglomerating dispersion may optionally contain one or more of theabove acrylic ester copolymers.

The concentration of the acrylate copolymers in the dispersion used forthe agglomeration is generally between 3 and 40 wt.-%. For theagglomeration from 0.2 to 20, preferably 1 to 5 parts by weight of theagglomerating dispersion are used based on 100 parts of the rubberlatex, in each case calculated on the solids content. The agglomerationis carried out by adding the agglomerating dispersion to the rubber. Theaddition rate usually is not critical, in general it takes about 1 to 30minutes at a temperature between 20 and 90° C., preferably between 30and 75° C.

Particular preference is given to the agglomeration of the rubber latex(graft base a₁) with an acid, preferably with an acid anhydride and morepreferably acetic anhydride (see WO 2012/022710, p. 9-10). Preferablythe rubber latex a₁ is mixed with said acid, and after agglomeration iscomplete, preferably restabilization with a base, preferably a potassiumhydroxide solution, alone or in combination with an emulsifier solutionsuch as Sodium or Potassium naphthalene sulfonate formaldehydecondensates or rosin soap is carried out. Preferred for therestabilization is a combination of potassium hydroxide solution withsodium or potassium naphthalene sulfonate formaldehyde condensates orrosin soap.

Preferably, acetic anhydride is used for this agglomeration. However,other organic anhydrides can also be used. It is also possible to usemixtures of acetic anhydride with acetic acid or mixtures of organicanhydrides with acetic acid or other carboxylic acids.

Once the agglomeration is complete, the agglomerated rubber latex ispreferably restabilized with a base such as potassium hydroxide solutionalone, or, preferably in combination with an emulsifier solution such assodium or potassium naphthalene sulfonate formaldehyde condensates orrosin soap, so that the result is a pH value of preferably more than pH7.5. Other alkaline solutions, such as, e.g., sodium hydroxide solution,can be used, albeit this is less preferred.

According to a preferred embodiment first, the starting rubber latex isprovided, wherein, in a preferred form, the solid content of the solidof this latex is adjusted to from 25 to 45 wt.-% by the addition ofwater. The temperature of the starting rubber latex, optionally mixedwith water, can be adjusted in a broad range of from 0° C. to 70° C.,preferably of from 0° C. to 60° C., and particularly preferably of from15° C. to 50° C.

Preferably at this temperature, a mixture of preferably acetic anhydrideand water, which was prepared by mixing, is added to the starting rubberlatex under good mixing. The addition of the acetic anhydride-watermixture and the mixing with the starting rubber latex should take placewithin a time span of two minutes at most in order to keep the coagulateformation as small as possible. The coagulate formation cannot beavoided completely, but the amount of coagulate can be limitedadvantageously by this measure to significantly less than 1 wt.-%,generally to significantly less than 0.5 wt.-% based on the solids ofthe starting rubber latex used.

Preferably the mixing ratio of the acetic anhydride-water mixture usedin the agglomeration step is 1:7.5 to 1:40, preferably 1:10 to 1:30,more preferably 1:15 to 1:30. When the acetic anhydride-water mixture isadded, agglomeration of the fine-particle rubber particles within thestarting rubber latex to form larger rubber particles starts and isfinished after 5 to 60 minutes according to the adjusted temperature.The rubber latex is not stirred or mixed in this phase. Theagglomeration, the increase in size of the rubber particles, comes to astandstill when the entire amount of acetic anhydride is hydrolyzed andthe pH value of the rubber latex does not drop any further. Forrestabilization, again preferably potassium hydroxide solution or,preferably in combination with an emulsifier solution as beforementioned, is carefully added to the rubber latex and mixed with therubber latex, so that a pH value of the rubber latex of at least pH 7.5results.

According to a further preferred embodiment, the agglomeration step iscarried out by the addition of 0.1 to 5 parts by weight of acetic acidanhydride per 100 parts of the starting rubber latex solids. Thestarting rubber latex solids means here a solid content of preferably 25to 45 wt.-% (evaporation sample at 180° C. for 25 min. in dryingcabinet), more preferably 30 to 45 wt.-%, particularly preferably 35 to45 wt.-%.

Furthermore agglomeration by pressure or freezing (pressure or freezeagglomeration) is possible. Said methods mentioned are known to a personskilled in the art.

The gel contents of the graft base a₁ may in principle be adjusted in amanner known per se by employing suitable reaction conditions (e.g. highreaction temperature and/or polymerization up to a high conversion, aswell as optionally the addition of crosslinking substances in order toachieve a high gel content, or for example low reaction temperatureand/or termination of the polymerization reaction before a too highdegree of crosslinking has occurred, as well as optionally the additionof molecular weight regulators, such as for example n-dodecyl mercaptanor t-dodecyl mercaptan in order to achieve a low gel content).

Usually, the polymerization of the graft base a₁ is performed byselecting the reaction conditions, so that a graft base a₁ with aspecific crosslinking state is obtained. Essential parameters thereforare inter alia the reaction temperature and time, the ratio of monomers,regulators, free-radical initiators and, for example in the feedprocess, the feed rate and the amount and time of addition of regulatorand initiator.

The crosslinking state of the graft base a₁ can be measured by the gelcontent which is the product portion, which is crosslinked and thus notsoluble in a particular solvent. The values given for the gel contentrelate to the determination by the wire cage method in toluene (seeHouben-Weyl, Methoden der Organischen Chemie, Makromolekulare Stoffe,Part 1, p. 307 (1961), Thieme Verlag Stuttgart).

Usual gel contents of the graft bases a₁ used in the invention are inthe range from 60 to 98%, preferably 65 to 98%, more preferably 70 to97%, most preferably 75 to 95%. Preferably the gel content of the graftbase a₁ is 70 to 97%, preferred 75 to 95% and the swelling degree of thegel in toluene is in the range of 15 to 35, preferably in the range of18 to 33.

The preparation of the graft a₂ grafted onto the graft base a₁ can beperformed under the same conditions as the preparation of the graftingbase a₁, in doing so it being possible to produce the graft a₂ in one ormore process steps. Further details for the preparation of graftcopolymers A are described in DE 12 60 135 and WO 2012/022710. The graftpolymerization of the monomers a₂₁, a₂₂ and a₂₃ is also carried out in afree-radical emulsion polymerization technique. It may be carried out inthe same system as the polymerization of the graft base a₁, and furtheremulsifier and initiator may be added.

These need not be identical with the emulsifiers or initiators used forpreparing the graft base a₁. For the selection of emulsifier, initiator,regulator etc. the same remarks apply as for the preparation of thegraft base a₁. The monomer mixture to be grafted can be added to thereaction mixture all at once, batch-wise in several stages, orpreferably, continuously during the polymerization.

As far as during the grafting of the graft base a₁ non-grafted polymersof the monomers a₂₁ to a₂₂ are obtained, their amounts are assigned tothe weight of component A. Said amounts are generally in the range offrom 10 to 50%, based on a₂.

Preferably at least one graft copolymer A is used obtained by emulsionpolymerization of

a₁: 40 to 90 wt.-%, preferably 45 to 85 wt.-%, based on (A),particularly preferably 45 to 75 wt.-% of at least one graft base a₁made from:

-   -   (a₁₁) 80 to 98 wt.-%, preferably 85 to 97 wt.-%, based on a₁, of        1,3-butadiene,    -   (a₁₂) 2 to 20 wt.-%, preferably 3 to 15 wt.-%, based on a₁, of        styrene; and

a₂: 10 to 60 wt.-%, preferably 15 to 55 wt.-%, based on (A),particularly preferably 25 to 55 wt.-% of a graft a₂, grafted onto thegraft base a₁ and built up from:

-   -   a₂₁: 65 to 80 wt.-%, in particular 65 to 75 wt.-%, based on a₂,        of styrene; and    -   a₂₂: 20 to 35 wt.-%, in particular 25 to 35 wt.-%, based on a₂,        of acrylonitrile.

Component B

Component B forms a polymer “hard phase” having a glass transitiontemperature Tg of >20° C., measured by dynamic mechanical analysis (DMA)using a frequency of 1 Hz. Preferably component B is at least onecopolymer B obtained by polymerization of styrene or α-methylstyrene(b1) and acrylonitrile (b2), a so-called SAN-copolymer or AMSANcopolymer. SAN-copolymers are even more preferred.

Said SAN and AMSAN copolymers generally are made from 18 to 40 wt.-%,preferably 22 to 33 wt.-%, particularly preferably 25 to 31 wt.-% ofacrylonitrile, and 82 to 60 wt.-%, preferably 78 to 67 wt.-%,particularly preferably 75 to 69 wt.-% styrene or α-methylstyrene,wherein the sum of styrene or α-methylstyrene and acrylonitrile totals100 wt.-%.

Component B, in particular said at least one SAN- or AMSAN-copolymer,preferably has a weight average molar mass M_(w) of from 85,000 to300,000 g/mol, more preferably from 120,000 to 250,000 g/mol and mostpreferably from 140,000 to 230,000 g/mol, measured by gel permeationchromatography and using polystyrene for calibration. Preferablycomponent B is a mixture of at least two, preferably two, three, four orfive, SAN-copolymers having different weight average molar masses M_(w)in the aforementioned ranges.

Copolymers B are obtained in a known manner by bulk, solution,suspension, precipitation or emulsion polymerization, bulk, suspensionand solution polymerization are preferred. Details of these processesare described, for example in “Kunststoffhandbuch, Eds. R. Vieweg and G.Daumiller, Vol. 4 “Polystyrol”, Carl Hanser Verlag, Munich 1996, p 104ff and in “Modern Styrenic Polymers: Polystyrenes and Styreniccopolymers” (Eds., J. Scheirs, D. Priddy, Wiley, Chichester, UK, (2003),pages 27 to 29) and in GB-A 1,472,195. The melting volume rate (MVR,measured according to ISO 1133 at 220° C. and 10 kg load) of componentB, in particular of the at least one SAN-copolymer as defined above, ispreferably at least 3 mL/10 min, more preferably in the range of from 3to 20 mL/10 min. Preferably component B is a mixture of at least two,preferably two, three, four or five, copolymers B, preferablySAN-copolymers B, with different MVRs in the range of from 3 to 90 mL/10min. The ratio of said at least two, preferably two, three, four orfive, copolymers B, preferably SAN-copolymers B, with different MVR ischosen so, that the resulting MVR of the mixture is preferably in therange of from 3 to 20 mL/10 min.

Component C

Preferably the at least one—preferably one—copolymer C is made from:

-   -   70 to 85% by weight, based on (C), ethylene (c₁),    -   15 to 30% by weight, based on (C), at least one, preferably one,        C₁-C₆-alkyl(meth)acrylate (c₂), preferably C₁-C₆-alkylacrylate,        more preferred methyl-, ethyl- and/or n-butylacrylate, most        preferred methyl- and/or ethylacrylat, in particular        methylacrylate, and    -   0 to 10% by weight, based on (C), of at least one further        comonomer (c₃) which is copolymerizable with (c_(i)) and (c₂),        preferably selected from the group consisting of: carbon        monoxide, alpha-olefins such as propene and/or (meth)acrylic        acid, glycidyl (meth)acrylate.

Alkyl(meth)acrylate (c₂) means an alkyl ester of acrylic or methacrylicacid. The alkyl group of the acrylic or methacrylic acid ester maycontain from 1 to 6 carbon atoms and means in particular methyl, ethyl,propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, isobutyl and isoamyl,with the preferred esters being the methyl and the ethyl esters.

Preferably copolymer C is made from ethylene (c₁) and methylacrylate(c₂).

Said copolymers C can be prepared by known methods as disclosed, forexample, in U.S. Pat. No. 3,350,372, the disclosure of which isincorporated herein by reference.

Preferably the Melt Flow Rate (MFR) of component C is 0.5-50 g/10 min(190° 012.16 kg) (ASTM D1238; ISO 1133-1:2011), more preferred 0.5 to 10g/10 min. Component C generally has a weight average molar mass M_(w) ofless than 1,000,000 g/mol, preferably less than 700,000 g/mol, morepreferred less than 500,000 g/mol. Suitable and preferred copolymers Care commercially available as Elvaloy® AC from DuPont®, the Elvaloy ACethylene-methylacrylates being in particular preferred, in particularthose which comprise only ethylene and methylacrylates units.

Component D

Graft rubber copolymer D as described above is preferably built up from

-   -   (d₁) from 12 to 20% by weight, based on (D), of a graft base        (d₁), and    -   (d₂) from 80 to 88% by weight, based on (D), of a graft (d₂),        grafted onto the graft base.

Preferred is a graft rubber copolymer D as described above whereincomponent d₂₃ is not present. Furthermore preferred is a graft rubbercopolymer D as described above wherein component d₁₁ is 1,3-butadiene.Furthermore preferred is a graft rubber copolymer D as described abovewherein component d₁₂ is styrene. Furthermore preferred is a graftrubber copolymer D as described above wherein component d₂₁ is styrene.Furthermore preferred is a graft rubber copolymer D as described abovewherein component d₂₂ is acrylonitrile.

More preferred is graft rubber copolymer D as described above built upfrom:

-   -   (d₁) 10 to 25%, preferably 12 to 20%, by weight, based on (D),        of a graft base (d₁) made from        -   (d₁₁) 75 to 100% by weight, based on (d₁), 1,3-butadiene,            and        -   (d₁₂) 0 to 25% by weight, based on (d₁), styrene; and    -   (d₂) 75 to 90%, preferably 80 to 88% by weight, based on (D), of        a graft (d₂), grafted onto the graft base and built up from        -   (d₂₁) 68 to 82%, preferably 70 to 80%, by weight, based on            (d₂), styrene,        -   (d₂₂) 18 to 32%, preferably 20 to 30%, by weight, based on            (d₂), acrylonitrile.

The graft base d₁ can be a linear polymer, a long-chain branched polymeror a star-branched polymer. Graft base d₁ generally is a soluble polymerwith no or negligible amount of insoluble parts. Comonomers d₁₁ and d₁₂can be polymerized statistically, in block form or in tapered form(gradient composition of d₁₁ and d₁₂).

Preferably graft base d₁ is obtained by anionic polymerization.

The mass polymerization is preferably conducted in a monomer mediumrather than in water, usually employing a series of two or morecontinuous reactors. The graft base (d₁) used in this process is mostcommonly a solution polymerized diene homo- or copolymer. Often asolution of the graft base (d₁) in the monomers (d₂₁) and (d₂₂) isprepared for feeding to the reactor system. It is also possible to useonly a part of the monomers (d₂₁) and (d₂₂) (fresh and unreactedmonomers from the devolatilization) and to feed the remaining part tothe reactors.

In the mass process, the graft base (d₁) initially dissolved in themonomer mixture will phase separate, forming discrete rubber particlesas polymerization of monomers (d₂₁) and (d₂₂) proceeds. This process isreferred to as phase inversion since the continuous phase shifts fromrubber to graft rubber copolymers D during the course of polymerization.Special reactor designs are used to control the phase inversion portionof the reaction. By controlling the shear rate in the reactor, therubber particle size can be modified to optimize properties. Grafting ofsome of the copolymerized monomers (d₂₁) and (d₂₂) onto the rubberparticles occurs. The reaction recipe can include polymerizationinitiators, chain-transfer agents, and other additives. Diluents aresometimes used to reduce the viscosity of the monomer and polymermixture to facilitate processing at high conversion. The reaction ispreferably carried out as a free radical-solution polymerization. Theproduct from the reactor system is usually devolatilized to remove theunreacted monomers and is then pelletized. Equipment used fordevolatilization includes single- and twin-screw extruders and flash andthin film/strand evaporators.

Unreacted monomers can be recovered and recycled back to the reactors toimprove the process yield.

The suspension polymerization process utilizes a mass reaction toproduce a partially converted mixture of polymer and monomer and thenemploys a batch suspension process to complete the polymerization. Whenthe conversion of the monomers is approximately 15 to 30% complete, themixture of polymer and unreacted monomers is suspended in water with theintroduction of a suspending agent. The reaction is continued until ahigh degree of monomer conversion is attained and then unreactedmonomers are usually stripped from the product before the slurry iscentrifuged and dried, producing product in the form of small beads. Themorphology and properties of the mass suspension product are similar tothose of the mass-polymerized product. The suspension process retainssome of the process advantages of the water-based emulsion process, suchas lower viscosity in the reactor and good heat removal capability.

In case that the graft rubber copolymer D is obtained by free-radicalsolution polymerization at least one solvent is used such as methylethylketone, acetone, toluene and/or ethylbenzene. Preferably the particlesof the graft rubber copolymer D) have a weight average particle sizeD_(w) in the range of 0.55 to 1.50 μm, preferably 0.60 to 1.00 μm.

Component E

Component E is at least one—preferably one—inorganic additive E selectedfrom phyllosilicates (E1) and nano calcium carbonate (E2).

If component E1 is present, it is preferably used in an amount of from0.01 to 5 pbw, more preferred 0.05 to 3 pbw, based on 100 parts byweight of the molding composition consisting of components A to D.

If component E2 is present, it is preferably used in an amount of from0.01 to 5 pbw, more preferred 0.05 to 5 pbw, based on 100 parts byweight of the molding composition consisting of components A to D.

Component E1 is a phyllosilicate. Suitable phyllosilicates aredescribed, by way of example, in Hollemann Wiberg, Lehrbuch deranorganischen Chemie, Walter de Gruyter, Berlin, N.Y. 1985, pp. 771-776.

Use is preferably made of serpentine types, such as chrytosile orantigorite, kaolinite types, such as dickite, nacrite, or halloysite,pyrophyllite, micaceous silicates from the vermiculite group, illitegroup, or montmorillonite/beidellite group, such as montmorillonite, orelse mica, or an aluminosilicate, such as muskovite, phlogopite, orbiotite. Very particular preference is given to mica. For the purposesof the present invention, kaolinite types include kaolin, the mainmineral of which is kaolinite, and mica-like silicates includebentonite, the main mineral of which is montmorillonite.

According to the invention nano calcium carbonate (E2) meansnano-particles of calcium carbonate (NPCC) with a mean size of less than100 nm, in particular a mean size of 15 to 60 nm, most preferred a meanparticle size of about 40 nm. The morphology of the nano-particle can beof different shape such as cubic, spindle, rod or flake, a cubic shapebeing preferred.

Suitable nano calcium carbonates can be obtained by High GravityControlled Precipitation (HGCP) technology and are commerciallyavailable from NanoMaterials Technology®.

Component F

Use may be made of other additives (different from component E) and/orprocessing aids as component F.

Examples of substances of this type are lubricants, mold-release agents,waxes, pigments, dyes, flame retardants, antioxidants, stabilizers tocounter the effect of light, fibrous or pulverulent fillers, fibrous orpulverulent reinforcing agents, and antistatic agents, and also otheradditives, and mixtures of these.

Examples of suitable lubricants and mold-release agents are stearicacids, stearyl alcohol, stearic esters, stearamides, and also siliconeoils, montan waxes, and those based on polyethylene or polypropylene.Said lubricants and mold release agents are generally used in amounts upto 3 parts by weight, preferably up to 2 parts by weight, based on 100parts by weight of the molding composition consisting of components A toD.

Examples of pigments are titanium dioxide, phthalocyanines, ultramarineblue, iron oxides, and carbon black, and the entire class of organic andinorganic pigments. For the purposes of the present invention, dyes areany of the dyes which can be used for the transparent, semitransparent,or non-transparent coloring of polymers, in particular those dyes whichare suitable for coloring styrene copolymers. Dyes of this type areknown to the skilled worker. Said pigments and dyes are generally usedin amounts up to 20 pbw, preferably up to 10 pbw, based on 100 parts byweight of the molding composition consisting of components A to D.

Examples of suitable flame retardants are antimony oxides, such asSb₂O₃, and/or halogenated organic compounds.

Particularly suitable antioxidants are sterically hindered mononuclearor polynuclear phenolic antioxidants, which may have varioussubstituents and may also have bridging by substituents. These includeboth monomeric and oligomeric compounds, which may have been built upfrom two or more phenolic building blocks. It is also possible to usehydroquinones or hydroquinone analogs, or substituted compounds, or elseantioxidants based on tocopherols or on derivatives of these. It is alsopossible to use mixtures of various antioxidants. Usually saidantioxidants are used in amounts up to 1 pbw, based on 100 parts byweight of the molding composition consisting of components A to D. Inprinciple, use may be made of any compounds which are commerciallyavailable or are suitable for styrene copolymers.

Together with the phenolic antioxidants mentioned above by way ofexample, concomitant use may be made of what are known as costabilizers,in particular phosphorus- or sulfur-containing costabilizers. These P-or S-containing costabilizers are known to the skilled worker and areavailable commercially.

Examples for suitable antioxidants are:

Esters of 3,5-di-tert.-butyl-4-hydroxyphenylacetic acid with monohydricor polyhydric alcohols, such as for example and preferably decanol,undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol,hexadecanol, octadecanol, 1,6-hexanediol, neopentyl glycol,1,9-nonanediol, ethylene glycol, diethylene glycol, triethylene glycol,pentaerythritol, 3-thiaundecanol, 3-thiapentadecanol, trimethylolpropane;

Esters of β-(3,5-di-tert.-butyl-4-hydroxyphenyl)-propionic acid with theafore-mentioned monohydric or polyhydric alcohols; and

Esters of β-(5-tert.-butyl-4-hydroxy-3-methylphenyl)-propionic acid withmonohydric or polyhydric alcohols, with the afore-mentioned monohydricor polyhydric alcohols;

Esters of β-(3,5-dicyclohexyl-4-hydroxyphenyl)-propionic acid with theafore-mentioned monohydric or polyhydric alcohols.

Preferred antioxidants are 3,3′-thiodipropionic acid dioctadecylester(CAS-No. 693-36-7),octadecyl-3-(3,5-di-tert.butyl-4-hydroxyphenyl)-propionate (CAS-No.2082-79-3) and the butylated reaction product of p-cresol anddicyclopentadiene (CAS-No. 68610-51-5).

Examples of suitable stabilizers to counter the effect of light arevarious substituted resorcinols, salicylates, benzotriazoles,benzophenones, and HALS (hindered amine light stabilizers), for examplethose commercially available as Tinuvin.

Preferred are Tinuvin 770 DF 1,bis(2,2,6,6,-tetramethyl-4-piperidyl)sebaceate (CAS-No. 52829-07-9),Tinuvin P, 2-(2H-benzotriazol-2-yl)-p-cresol (CAS-No. 2440-22-4),Cyasorb UV 3853, 2,2,6,6-tetramethyl-4-piperidinyl stearate (CAS-No.167078-06-0), Hostavin N 845 (CAS-No. 86403-32-9) and mixtures thereof.

Said stabilizers are generally used in amounts up to 2 pbw, based on 100parts by weight of the molding composition consisting of components A toD.

Examples of fibrous or pulverulent fillers are carbon fibers and glassfibers in the form of glass wovens, glass mats, or glass silk rovings,chopped glass, glass beads, and also wollastonite, particularlypreferably glass fibers. When glass fibers are used, these may have beenprovided with a size and with a coupling agent to improve compatibilitywith the components of the blend. The glass fibers incorporated mayeither be in the form of short glass fibers or else in the form ofcontinuous strands (rovings). Said filler materials usually are used inamounts up to 20 pbw, preferably up to 10 pbw, based on 100 parts byweight of the molding composition consisting of components A to D.

If not in particular mentioned, the amounts used of each of theadditives are those which are usual, and it is therefore unnecessary togive further details in this connection.

Preparation of the Molding Compositions

The preparation of the thermoplastic molding compositions followsconventional procedures which are well known in the art. Preferably, thecomponents A to C and optional components D to F are extrusion blendedor compounded in conventional mixing apparatuses (preferably inmulti-cylinder mills, mixing extruders or internal kneaders).

Preferably components A, B and C and, optionally, components D to F aremixed and compounded and extruded at elevated temperature, generally attemperatures of from 150° C. to 300° C. During the production, workingup, further processing and final shaping, the required or usefuladditives E and/or F can be added to the thermoplastic moldingcomposition. The final shaping can be carried out on commerciallyavailable processing machines, and comprises, for example,injection-molding processing, sheet extrusion with optionally subsequenthot forming, cold forming, extrusion of tubes and profiles and calenderprocessing.

A further aspect of the invention is a shaped article made from thethermoplastic molding composition. The thermoplastic molding compositioncan be formed into shaped articles by a variety of means such asinjection molding, extrusion, compression forming, vacuum forming, blowmolding etc. well established in the art. Preferred shaped articles aresheets formed by extrusion or layered sheets formed by co-extrusion.Said sheets can be used for thermoforming and can consist solely of thethermoplastic molding composition as described above or can have a layerstructure where at least one cap-layer consists of said moldingcomposition.

A further aspect of the invention is the use of shaped articles, inparticular thermoformed sheets, made from the thermoplastic moldingcompositions as described above in hydrofluoro olefin containing areas.Said shaped articles can advantageously be used as equipment liners(inliners) of cooling apparatuses, e.g. refrigerators. The thermoplasticmolding compositions as described above exhibit an improvedenvironmental stress crack resistance (ESCR) in presence of olefinicunsaturated blowing agents, in particular in presence of hydrofluoroolefins (HFO) as well as the favorable properties known for ABSmaterials and therefore are in particular suitable to manufacturethermoformed equipment liners of cooling apparatuses containinginsulation foamed with “Fourth Generation” blowing agents or mixturescontaining them.

The examples and claims below give further illustration of theinvention.

EXAMPLES Graft Rubber Copolymer A Preparation of the Graft Base a₁

The particulate cross-linked fine-particle rubber base used for thepreparation of component A (emulsion graft rubber copolymer) wasprepared by radical emulsion polymerization of butadiene and styrene(monomer weight ratio 90/10) in the presence of distilled tallow fattyacid (CAS-No. 67701-06-8, C14-C18-saturated and C15-C18-unsaturatedstraight chain aliphatic monocarboxylic acid), tert-dodecylmercaptan aschain transfer agent, potassium persulfate as initiator at temperaturesfrom 60° to 85° C. As salt tetrasodium pyrophosphate is used.

The addition of initiator marked the beginning of the polymerization.Finally the fine-particle butadiene rubber latexes are cooled below 50°C. and the non-reacted monomers were removed partially under vacuum (200to 500 mbar) at temperatures below 50° C. which defines the end of thepolymerization.

The starting styrene/butadiene-rubber (SBR) rubber base so obtained hassolid content of 41 wt.-%, a rubber gel content of 93% (wire cage methodin toluene), a rubber composition comprising units derived from styreneand butadiene in a weight ratio of 10/90 and a weight-average particlesize of 0.08 μm (determined via Differential Centrifugation using a disccentrifuge from CPS Instruments). The starting SBR was subjected toparticle size enlargement with acetic anhydride in two batches to aweight-average particle size D_(w) of 0.25 μm and 0.55 μm, respectively.

In order to achieve agglomerated butadiene rubber latices with D_(w) of0.25 μm, the fine-particle butadiene rubber latexes are being providedfirst at 25° C. and are adjusted if necessary with deionized water to aconcentration of 36 wt.-% and stirred. The temperature was raised to 40°C. To this dispersion, 1.3 weight parts of acetic anhydride based on 100parts of the solids from the fine-particle butadiene rubber latex asaqueous mixture is added and mixed with the latex. After this theagglomeration is carried out for 10 minutes without stirring.

Anionic dispersant of sulfonic polyelectrolyte type (Sodium naphthalenesulfonate formaldehyde condensates, CAS 9084-06-04) are added as aqueoussolution to the agglomerated latex and mixed by stirring. SubsequentlyKOH are added as aqueous solution to the agglomerated latex and mixed bystirring. The solid content of the agglomerated butadiene rubber latexwith D_(w) of 0.25 μm is 28.5 wt.-%.

In order to achieve agglomerated butadiene rubber latices with D_(w) of0.55 μm, the fine-particle butadiene rubber latices are being providedfirst at 25° C. and are adjusted if necessary with deionized water to aconcentration of 33 wt. % and stirred. To this dispersion, 2 weightparts of acetic anhydride based on 100 parts of the solids from thefine-particle butadiene rubber latex as aqueous mixture is added andmixed with the latex. After this the agglomeration is carried out for 30minutes without stirring. Anionic dispersant of sulfonic polyelectrolytetype (Sodium naphthalene sulfonate formaldehyde condensates, CAS9084-06-04) are added as aqueous solution to the agglomerated latex andmixed by stirring. Subsequently KOH are added as aqueous solution to theagglomerated latex and mixed by stirring. The solid content of theagglomerated butadiene rubber latex with D_(w) of 0.55 μm is 24.7 wt.-%.The two latexes with 0.25 μm (80 pts.) and 0.55 μm (20 pts.) werecombined to rubber base a1 which is used in the further reaction step inform of polymer latexes which have solids content of 26 wt.-%.

Preparation of the Graft Rubber Copolymer A

The graft copolymer A is prepared (as parts by weight) from 52styrene/butadiene-rubber (SBR), 34 styrene, 14 acrylonitrile, togetherwith cumene hydroperoxide, dextrose, ferrous sulfate,t-dodecylmercaptane, disproportionated potassium rosinate soap, andemulsion graft polymerization was conducted. Firstly, theafore-mentioned SBR latex a₁ was charged, and the temperature was raisedto 70° C. Styrene, acrylonitrile, t-dodecylmercaptane, disproportionatedpotassium rosinate soap and deionized water were added. At 70° C., thecatalyst solution (sodium pyrophosphate, dextrose, cumene hydroperoxideand ferrous sulfate dissolved in water) was added. After completion ofthe addition, the stirring was continued for further 30 minutes, andthen the mixture was cooled. To the graft copolymer latex thus obtained,an aging-preventive agent (e.g. Antioxidant PL/Wingstay L, Phenol,4-methyl-, reaction products with dicyclopentadiene and isobutene,CAS-No. 68610-51-5) was added, and the mixture was added under stirringto an aqueous magnesium sulfate solution heated to 95° C., forcoagulation. The coagulated product was washed with water and dried toobtain a high rubber content resin composition in the form of a whitepowder.

Preparation of the Matrix Copolymer B

Statistical SAN-copolymer B1 was produced by suspension polymerizationfrom 72 wt.-% styrene and 28 wt.-% acrylonitrile with a weight averagemolar mass of 230,000 kg/mol (determined by gel permeationchromatography and using polystyrene for calibration) and MVR of 3.5cm³/10 min (220° C./10 kg load (ISO 1133-1:2011)).

Statistical SAN-copolymer B2 was produced by suspension polymerizationfrom 66 wt.-% styrene and 34 wt.-% acrylonitrile with a weight averagemolar mass of 89,000 kg/mol (determined by gel permeation chromatographyand using polystyrene for calibration) and MVR of 75 cm³/10 min (220°C./10 kg load (ISO 1133-1:2011)).

Statistical SAN-copolymer B3 was produced by suspension polymerizationfrom 66 wt.-% styrene and 34 wt.-% acrylonitrile with a weight averagemolar mass of 180,000 kg/mol (determined by gel permeationchromatography and using polystyrene for calibration) and MVR of 3cm³/10 min (220° C./10 kg load (ISO 1133-1:2011)).

Statistical SAN-copolymer B4 was produced by mass polymerization from 69wt.-% styrene and 31 wt.-% acrylonitrile with a weight average molarmass of 140,000 kg/mol (determined by gel permeation chromatography andusing polystyrene for calibration) and MVR of 19 cm³/10 min (220° C./10kg load (ISO 1133-1:2011)).

Statistical SAN-copolymer B5 was produced by suspension polymerizationfrom 69 wt.-% styrene and 31 wt.-% acrylonitrile with a weight averagemolar mass of 200,000 kg/mol (determined by gel permeationchromatography and using polystyrene for calibration) and MVR of 4cm³/10 min (220° C./10 kg load (ISO 1133-1:2011)).

Preparation of Graft Rubber Copolymer D (mABS)

Continuous mass ABS copolymer D was produced by free-radical solutionpolymerization from 17% butadiene, 63% styrene, 20% acrylonitrile byweight in the presence of methylethyl ketone with a gel content of 30%(acetone method), a weight average particle size of the grafted rubberof 0.6 to 1 μm (determined via Differential Centrifugation using a disccentrifuge from CPS Instruments) and a MVR of 5.5 cm³/10 min (ISO1133-1:2011).

The gel content was determined in acetone or toluene as dispersant.Approximately, 0.25 g of the polymer composition were dispersed in 20 gof dispersant for 12-24 h and separated with an ultracentrifuge at20,000 rpm at 25° C. into the gel and sol phase. The separated phaseswere dried and the gel content is calculated by the following formula:gel=mass(gel phase)/(mass(gel phase)+mass(sol phase))*100[%]

Preparation of the Thermoplastic Molding Compositions

In the following examples and comparative examples, the afore-mentionedcopolymers A, B and D and the following components C and F were used inthe amounts as given in Table 1. The additives and processing aids(component F) were added to 100 parts by weight (pbw.) of the polymercomponents as listed in Table 1 (left column).

Component C: Elvaloy® AC 1224: a copolymer of ethylene and methylacrylate containing 24% by weight methyl acrylate, produced by DuPont;melt flow rate (190° C./2.16 kg) 2.0 g/10 min (ISO 1133/ASTM D1238),density 0.944 g/cm³ (ASTM D792/ISO 1183), melting point by DSC 91° C.(ISO 3146/ASTM D3418), Vicat Softening Point 48° C. (ASTM D1525/ISO306).

F1: Ethylene bis stearamide, CAS-No. 110-30-5

F2: Silicone oil, 60,000 cSt, polydimethylsiloxane, CAS-No. 63148-62-9

F3: Thiosynergic heat stabilizer, 3,3′-thiodipropionic aciddioctadecylester, CAS-No. 693-36-7

F4: Phenolic primary antioxidant,octadecyl-3-(3,5-di-tert.butyl-4-hydroxyphenyl)-propionate, CAS-No.2082-79-3

F5: Titanium dioxide CAS-No. 13463-67-7

The components A, B, C and D according to Table 1 and theafore-mentioned additives and processing aids F were compounded underthe following conditions: Extruder Machine L/D: 30, diameter: 40 mm,co-rotating twin screw, manufacture: KraussMaffei Berstorff, Germany,die head and melt temp: 250° C., throughput: 50˜60 kg/h.

The thermoplastic compositions were tested using the following methods:

Notched Charpy impact strength [kJ/m2]:

The notched Charpy impact strength is measured on test specimen (80×10×4mm, injection molded at a mass temperature of 240° C. and a moldtemperature of 70° C.), at 23° C. according to ISO 179-1A.

Notched Izod impact strength [kJ/m²]:

The notched Izod impact strength [kJ/m²] is measured on test specimen(80×10×4 mm, injection molded at a mass temperature of 240° C. and amold temperature of 70° C.), at 23° C. according to ISO 180-1A.

Melt volume index (MVR [ml/10 min]):

The melt volume rate MVR is measured on a polymer melt at 220° C. and 10kg load according to ISO 1133.

Tensile strain at break [%]:

The tensile strain at break [%] is measured on Dumbbell test specimen170×10×4 mm (injection molded at a mass temperature of 240° C. and amold temperature of 70° C.) at 23° C. according to DIN EN ISO 527.

ESCR method:

After compounding, the obtained thermoplastic compositions wereinjection molded into test bars with the dimension 80×10×4 mm underfollowing conditions: Clamping force: 120 MT, manufacturer: Dongshing,Korea, injection temperature: 240° C., Injection speed: 60%, cycle time:45 sec, mold temp: 60° C. The molded bars were tested in regard to theirchemical resistance according to the following environmental stresscrack resistance (ESCR) test:

Injection molded test bars (80×10×4 mm) are mounted on a jig whichmaintains constant curvature at 2.5% outer fiber strain. The jig withthe test pieces is placed into a jar filled with the chemical agent in away that the test bars are completely covered. During the experiment,the proceeding degradation is monitored and reviewed in dependence oftime. After allowing the test pieces to stand in the prescribedenvironmental conditions for a specific period of time (in normal case300 min or till complete crack) and removing them from the jig, thecondition of physical degradation is checked.

The determination of chemical resistance was done optically independence of the following criteria: complete crack, partial crack,surface crack, edge crack, and surface quality after aging.

A summary (cp. Table 2) is then given by the following symbols: X:degraded ▴: highly affected ▴▴: affected ▴▴▴: a little affected ▴▴▴▴:not affected (▴): 0.5 ▴

Table 1 describes the components of the thermoplastic compositions.

To better compare different materials also a ranking (cp. Table 2) isgiven (1=material with highest chemical resistance of all testedmaterials, 2=material with second highest chemical resistance of alltested materials, etc.).

Common chemicals for testing like cyclopentane were applied at roomtemperature. In case of trans-1-chloro-3,3,3-trifluoropropene (b.p. 19°C.) the tests were done at 0° C. to prevent evaporation of the agentwhile maintaining constant test conditions.

By comparison of the thermoplastic compositions according to theinventive examples 1 and 2 to the thermoplastic compositions ofcomparative examples Cp. 1 and Cp. 2, known from the prior art, it isfound that the thermoplastic molding compositions according to inventiveexamples 1 and 2 show superior ESCR behavior during the applied test.Inventive example 1 does not only show very good resistance againsttrans-1-chloro-3,3,3-trifluoropropene but also superior resistanceagainst cyclopentane. This is important since manufacturers use mixturesof blowing agents for their applications in most cases.

The chemical resistance against both tested blowing agents of thethermoplastic composition according to inventive example 2 is extremelygood.

Additionally, inventive examples 1 and 2 both show the favorableproperties known for ABS materials; good processability (MVR, elongationat break) and toughness (impact strength).

TABLE 1 Thermoplastic compositions Composition SAN-copolymer (B) graftmABS Elvaloy AN (IR, MVR 220/10 Additives (F) ABS (A) (D) (C) average)[cm³/10 min] F1 F2 F3 F4 F5 No. Components parts parts parts parts [%](average) parts parts parts parts parts Cp. 1 (A) + (B) 29 71 (9 B1 + 4032 18.3 1 0.25 0.25 0.5 7.8 B3 + 22 B4) 1 (A) + (B) + (C) 23 10 67 (53B1 + 29 6.7 1 0.25 0.5 0.5 5.5 14 B4) Cp. 2 (A) + (B) + (D) 20 20 60 (60B5) 31 4.1 3 0.2 0.5 0.5 5.5 2 (A) + (B) + 20 10 10 60 (60 B5) 31 4.1 30.2 0.5 0.5 5.5 (C) + (D)

TABLE 2 ESCR results and mechanical data ESCR test results Mechanicaldata Composition trans-1- notched notched MVR graft SAN-co-chloro-3,3,3- IZOD Charpy Elonga- (220° C., ABS mABS Elvaloy polymerCyclopentane trifluoropropene Impact Impact tion at 10 kg) Com- (A) (D)(C) (B) chemical rank- chemical rank- strength strength break [ml/ No.ponents parts parts parts parts resistance ing resistance ing [kJ/m²][kJ/m²] [%] 10 min] Cp. 1 (A) + (B) 29 71 ▴ ▴ ▴ (▴) 2 ▴ ▴ 3 31.8 26.424.8 4.4 1 (A) + 23 10 67 ▴ ▴ ▴ ▴ 1 ▴ ▴ ▴ 2 35.2 — 50.0 5.0 (B) + (C)Cp. 2 (A) + 20 20 60 ▴ ▴ ▴ (▴) 2 ▴ ▴ ▴ 2 37.4 26.7 53.1 5.0 (B) + (D) 2(A) + (B) + 20 10 10 60 ▴ ▴ ▴ ▴ 1 ▴ ▴ ▴ (▴) 1 38.1 33.9 64.0 7.7 (C) +(D)

The invention claimed is:
 1. A method in which a thermoplastic moldingcomposition is formed into a shaped article requiring resistance tohydrofluoro olefins, wherein the thermoplastic molding compositioncomprises components A, B, C, and D: (A) 10 to 35 wt.-% of at least onegraft rubber copolymer A obtained by emulsion polymerization and builtup from: (a₁) 30 to 90 wt.-%, based on (A), of at least one graft base(a₁) made from: (a₁₁) 70 to 98 wt.-%, based on (a₁), of at least onediene, and (a₁₂) 2 to 30 wt.-%, based on (a₁), of at least one monomerselected from the group consisting of styrene, α-methylstyrene,acrylonitrile, methacrylonitrile, and methyl methacrylate, and (a₂) 10to 70 wt.-%, based on (A), of a graft (a₂), grafted onto the graft baseand built up from: (a₂₁) 65 to 95 wt.-%, based on (a₂), of at least onevinylaromatic monomer, (a₂₂) 5 to 35 wt.-%, based on (a₂), ofacrylonitrile and/or methacrylonitrile, and (a₂₃) 0 to 20 wt.-%, basedon (a₂), of at least one monomer selected from the group consisting ofC₁-C₄-alkyl(meth)acrylates, maleic anhydride, N-phenyl maleimide,N-cyclohexyl maleimide, and (meth)acrylamide; (B) 50 to 75 wt.-% of atleast one copolymer B made from: (b₁) 50 to 95 wt.-%, based on (B), ofat least one vinylaromatic monomer, (b₂) 5 to 50 wt.-%, based on (B), ofacrylonitrile and/or methacrylonitrile, and (b₃) 0 to 20 wt.-%, based on(B), of one or more of the monomers as described for (a₂₃); (C) 4 to 20wt.-% of at least one copolymer C made from (c₁) 70 to 91 wt.-%, basedon (C), of ethylene, (c₂) 9 to 30 wt.-%, based on (C), at least oneC₁-C₆-alkyl(meth)acrylate, and (c₃) 0 to 15 wt.-%, based on (C), of atleast one further comonomers copolymerizable with (c₁) and (c₂); and (D)4 to 20 wt.-% of at least one graft rubber copolymer D obtained by masspolymerization and built up from: (d₁) 10 to 25 wt.-%, based on (D), ofat least one graft base (d₁) made from: (d₁₁) 75 to 100 wt.-%, based on(d₁), of at least one diene, and (d₁₂) 0 to 25 wt.-%, based on (d₁), ofat least one vinylaromatic monomer, and (d₂) 75 to 90 wt.-%, based on(D), of a graft (d₂), grafted onto the graft base and built up from:(d₂₁) 68 to 82 wt.-%, based on (d₂), of at least one vinylaromaticmonomer, (d₂₂) 18 to 32 wt.-%, based on (d₂), of acrylonitrile ormethacrylonitrile, and (d₂₃) 0 to 20 wt.-%, based on (d₂), of one ormore of the monomers as described for (a₂₃); wherein the sum ofcomponents A, B, C, and D totals 100 wt.-%.
 2. The method according toclaim 1, wherein the thermoplastic molding composition further comprises0.01 to 20 parts by weight of at least one further additive and/orprocessing aid F, based on 100 parts by weight of the compositionconsisting of components A, B, C, and D.
 3. The method according toclaim 1, wherein the thermoplastic molding composition further comprises0.01 to 10 parts by weight of at least one inorganic additive E selectedfrom phyllosilicates (E1) and nano calcium carbonate (E2), based on 100parts by weight of the composition consisting of components A, B, C, andD.
 4. The method according to claim 1, wherein the thermoplastic moldingcomposition comprises components A, B, C, and D in the followingamounts: (A): 18 to 28 wt.-%; (B): 55 to 70 wt.-%; (C): 6 to 15 wt.-%;and (D): 6 to 15 wt.-%.
 5. The method according to claim 1, whereingraft rubber copolymer A is built up from: (a₁) 40 to 90 wt.-% of atleast one graft base (a₁) made from: (a₁₁) 80 to 98 wt.-% of at leastone diene (a₁₁), and (a₁₂) 2 to 20 wt.-% of at least one monomer (a₁₂),and (a₂) 10 to 60 wt.-% of a graft (a₂), grafted onto the graft base(a₁) and built up from: (a₂₁) 65 to 80 wt.-% of at least onevinylaromatic monomer (a₂₁), (a₂₂) 20 to 35 wt.-% of acrylonitrileand/or methacrylonitrile (a₂₂), and (a₂₃) 0 to 20 wt.-% of at least onemonomer (a₂₃).
 6. The method according to claim 1, wherein copolymer Bis made from: (b₁) 60 to 82 wt.-% of styrene or α-methylstyrene, and(b₂) 18 to 40 wt.-% of acrylonitrile.
 7. The method according to claim1, wherein copolymer C has a weight average molar mass M_(w) of lessthan 1,000,000 g/mol.
 8. The method according to claim 1, whereincopolymer C has a MFR of from 0.5-50 [g/10 min] (190° C./2.16 kg load,according to ASTM D1238; ISO 1133-1:2011).
 9. The method according toclaim 1, wherein copolymer C is an ethylene methylacrylate copolymer.10. The method according to claim 1, wherein graft copolymer D is builtup from: (d₁) 12 to 20 wt.-% of a graft base (d₁) made from: (d₁₁) 75 to100 wt.-% of 1,3-butadiene, and (d₁₂) 0 to 25 wt.-% of styrene, and (d₂)80 to 88 wt.-% of a graft (d₂), grafted onto the graft base and built upfrom: (d₂₁) 68 to 82 wt.-%, based on (d₂), of styrene, and (d₂₂) 18 to32 wt.-%, based on (d₂), of acrylonitrile.
 11. The method according toclaim 3, wherein component E1 is present in an amount of from 0.01 to 5parts by weight, based on 100 parts by weight of the compositionconsisting of components A, B, C, and D.
 12. The method according toclaim 3, wherein component E2 is present in an amount of from 0.01 to 10parts by weight, based on 100 parts by weight of the compositionconsisting of components A, B, C, and D.
 13. The method according toclaim 1, wherein the thermoplastic molding composition is formed intothe shaped articles by extrusion or co-extrusion.
 14. The methodaccording to claim 1, wherein the shaped article is an inliner incooling apparatuses.
 15. A thermoplastic molding composition as definedin claim
 1. 16. The thermoplastic molding composition according to claim15, comprising components A, B, C, and D in the following amounts: (A):18 to 28 wt.-%; (B): 55 to 70 wt.-%; (C): 6 to 15 wt.-%; and (D): 6 to15 wt.-%.